LOUISVILLE, Kentucky – Research indicates that willow has the best biomass potential for Canadian climates.
It has potential for an annual average of 4.16 to 8.3 tonnes dry matter (DM) per acre in a three-year cutting rotation.
According to agricultural engineers at Laval University in Quebec, producers require the right harvest equipment to reach that potential.
The Laval team said the common method of harvesting willow is to cut and chip the whole tree. Although chipping allows quicker dry down, it also makes handling and transport more difficult. Commercial chippers are readily available for this job.
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Where handling and transport are an issue, European biomass tree farmers have found that willow can be cut and bundled. However, there are no such machines commercially available in North America.
Agriculture Canada and Laval engineers worked together to develop a harvesting machine that could be assembled using North American components. They developed criteria for a machine to cut, lightly shred and bale willow stems.
Laval carried out the engineering, fabrication and field tests of the prototype willow harvester in 2006.
The team choose a New Holland round baler as the platform. They replaced the narrow compression chamber belts with a single full-width belt to better contain the long stems within the chamber.
Four rotary saws were integrated into a disc mower frame and installed in front of the baler to handle trees up to three inches in diameter.
A modified hammer type shredder was placed between the saws and the baler to break the willow stems and make them more pliable. Finally, a swing-pivot tongue was added to offset the baler from the tractor’s driveline.
Five field trials were conducted and more than 90 round bales of willow had been harvested by the end of 2006.
Bale size was 0.99 to 1.54 metres in diameter. Average moisture content was 44 to 51 percent.
The continuous bale forming capacity was eight to five wet tonnes per acre. Considering idle time, wrapping time and turning time, the harvest capacity would be two to 3.5 wet tonnes per acre.
The prototype cutter/shredder/baler was assembled primarily with components intended for straw and hay. It will be based at the Prairie Farm Rehabilitation Administration Shelterbelt Centre in Indian Head, Sask.
Pete de Graaf, an agricultural engineer, says the harvester’s saw blades run horizontally just above ground, so it is important to watch for rocks that could damage the front cutting device.
Some biomass growers in Ireland have used conventional logging equipment such as feller bunchers. These machines use a giant hydraulic claw to grab a half-dozen or more standing trees, cut them off at the base at the same time with a horizontal blade and then stack them for drying.
He says this lets producers give their trees an extra year of growth if they want, and they can harvest all winter long without concern about mud, compaction and field rutting.
